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Micro-organisms can survive the most arid conditions here on Earth, raising hopes for life on planets like Mars.

In the driest corner of South America’s Atacama Desert, decades can pass without any rain falling at all or just a single rainfall. These conditions mean that salt in the soil is highly concentrated and there is very little organic matter.

Scientists have observed microbial life in Atacama, but they’ve never been sure if those organisms have travelled in on the wind or if they can actually live in the bone-dry desert.

Now, an international team led by Washing State University planetary scientist Dirk Schulze-Makuch has found that at least some of these tiny forms of life have adapted to life in the desert. The specialised bacteria are able to survive by going dormant for decades and then reactivating and reproducing when it eventually rains.

“It has always fascinated me to go to the places where people don’t think anything could possibly survive and discover that life has somehow found a way to make it work,” Schulze-Makuch said in a statement.

The team, whose study is published in Proceedings of the National Academy of Sciences, were lucky enough to be onsite in 2015 when it actually rained in the desert. They detected an explosion of biological activity in the soil after the rare shower and performed genomic analyses to identify different indigenous species of microbial life that were reproducing.

“In the past researchers have found dying organisms near the surface and remnants of DNA but this is really the first time that anyone has been able to identify a persistent form of life living in the soil of the Atacama Desert,” Schulze-Makuch said.

“We believe these microbial communities can lay dormant for hundreds or even thousands of years in conditions very similar to what you would find on a planet like Mars and then come back to life when it rains.”

Of course, conditions on Mars are very different to anywhere on Earth. But billions of years ago, the planet did have small oceans and lakes and if early life-forms developed there, they could be using similar survival tactics to stay buried on Mars.

“We know there is water frozen in the Martian soil and recent research strongly suggests nightly snowfalls and other increased moisture events near the surface,” he said. “If life ever evolved on Mars, our research suggests it could have found a subsurface niche beneath today’s severely hyper-arid surface.”

The goal of Schulze-Makuch’s research is to figure out how life-forms survive the toughest conditions, so we know what to look for on alien worlds. The next step is to look for life in the Don Juan Pond in Antarctica, a very shallow lake that is so salty it stays liquid at temperatures as low as -58 degrees Fahrenheit.